Lecture 7: Fish in ecosystems Flashcards
What role do fish play in nutrient cycling within ecosystems?
Fish act as nutrient sinks during growth, sequestering phosphorus and nitrogen, and they redistribute nutrients through excretion and biomass turnover.
How does temperature influence fish metabolism and energy budget
Temperature increases metabolic rates, leading to higher food consumption needs. Beyond optimal thresholds, energy efficiency and growth decline.
What is the bioenergetics model, and what does it describe?
It models fish energy allocation:
πΆ=π +π΄πΆπ+ππ·π΄+π΅+(πΉ+π)
where C is consumption, R is respiration, ACT is activity cost, SDA is digestion cost, B is biomass growth, and F+U is waste loss.
How do fish contribute to nutrient cycling in aquatic systems?
Fish excrete dissolved nutrients like phosphorus and nitrogen, supporting primary production, and act as sinks by storing nutrients in their tissues.
How do fish influence eutrophication processes?
Fish reduce phytoplankton biomass by preying on zooplankton grazers and cycling nutrients, which can exacerbate or alleviate eutrophication.
What are diel vertical migrations (DVM) in fish, and why are they important?
DVM is the daily movement of fish to deeper waters during daylight to avoid predators and upward at night to feed, affecting nutrient transport.
What happens to nutrient dynamics when fish are removed through fishing?
Nutrients stored in fish biomass (e.g., phosphorus and nitrogen) are removed from the ecosystem, potentially altering nutrient availability.
How do environmental stressors like hypoxia and low salinity impact fish?
Hypoxia reduces oxygen availability, increasing stress and reducing feeding and growth, while low salinity increases osmoregulatory costs.
How do cyanobacterial blooms impact fish?
Toxins like microcystins cause oxidative stress, liver damage, and mortality. Blooms also reduce food quality for fish, affecting growth and reproduction.
How do fish compete with phytoplankton for nutrients?
Fish growth and nutrient sequestration can reduce phosphorus in the water column, indirectly limiting phytoplankton blooms.
What tools are used to study fish roles in ecosystems?
Bioenergetics models for energy budgets.
Stable isotopes to trace nutrient cycling.
Hydroacoustics to measure fish biomass and distribution.
Biomarkers to monitor fish health.
What are the ecosystem consequences of Baltic cod decline?
Cod decline led to increases in mesopredator populations (e.g., sprat, sticklebacks), altering food web structure and nutrient cycling.
